About Notechord
Notechord is a pitch reference — all 128 MIDI notes, each with its frequency, wavelength and period, and each one you can actually hear. It is the one site in this network that is genuinely about music: the others borrow the harmony metaphor; this one keeps it.
The numbers aren't looked up; they're derived. One public formula fixes every pitch —
f = 440 × 2^((m − 69) / 12) Hz
— where m is the MIDI note number and MIDI 69 is A4, concert pitch, 440 Hz (the standard set internationally in 1939 and codified as ISO 16 in 1955). Middle C is MIDI 60 — 261.626 Hz. From that single rule the site computes the whole table, and the build fails if any stored value drifts: the generator and the validator are separate programs, so a bug in one can't hide in the other.
Every note plays as a pure sine tone through the Web Audio API, right in your browser — nothing is uploaded, nothing is recorded, and the same engine powers the keyboard on the home page.
A handful of famous notes carry a short, verified story — concert pitch, middle C and the octave-numbering trap, the piano's edges, the guitar and double-bass open strings, the ceiling and floor of MIDI. Anything that couldn't be checked was left out rather than guessed.
There are also 611 chords — every root crossed with every quality, each with its interval formula, its notes and its guitar and ukulele fingerings, and each one you can strum. The interval formulas are standard music theory, written by hand; a separate validator converts every stored fingering back to pitch classes and fails the build if any voicing sounds a note outside the chord's formula, so the theory and the fingerings can't quietly disagree.
Chord voicings from chords-db by David Rubert (MIT). The formulas, note names, diagrams and audio are this site's own.
Spotted an error, or want a tuning reference added? Email howdy@notechord.com.